Lipolysis of LDL with phospholipase A2 alters the expression of selected apoB-100 epitopes and the interaction of LDL with cells

Group IIA secretory phospholipase A 2 is an acute phase enzyme, co-expressed with serum amyloid A protein. Both are present in atherosclerotic lesions. We report that human normal and acute phase high density lipoproteins and low density lipoprotein are effective substrates for human group IIA phospholipase A 2 . The enzyme hydrolyzed choline and ethanolamine glycerophospholipids at the sn -2 position resulting in an accumulation of the corresponding lysophospholipids, including the unhydrolyzed alkyl and alkenyl ether derivatives. The hydrolysis of acute phase high density lipoprotein was 2-to 3-fold more rapid and intensive than of normal high density lipoprotein. The hydrolysis of lipoproteins was noted at enzyme concentration as low as 0.05 g/mg protein, which was within the range observed in the circulation in acute and chronic inflammatory diseases. The enzyme hydrolyzed the different molecular species of the residual glycerophospholipids in proportion to their mass, showing no preference for the release of arachidonic acid. Group IIA phospholipase A 2 preferentially attacked the hydroxy and hydroperoxy linoleates and possibly other oxygenated fatty acids, which were released from the glycerophospholipids at early times of incubation. There was no effect on the content or molecular species composition of the sphingomyelins or neutral lipids of the lipoproteins. In conclusion, human plasma lipoproteins are the first reported natural biological substrates for human group IIA phospholipase A 2 . The enhanced hydrolysis of acute phase high density lipoproteins is probably due to its association with serum amyloid A protein, which enhances the activity of the enzyme and may promote its penetration to the lipid monolayer. As sPLA 2 -induced hydrolysis of the lipoproteins leads to accumulation of lysophosphatidylcholine and potentially toxic oxygenated fatty acids, overexpression of this enzyme may be proatherogenic.-Pruzanski, W., E. Stefanski, F. C. de Beer, M. C. de Beer, P. Vadas, A. Ravandi, and A. Kuksis. Lipoproteins are substrates for human secretory group IIA phospholipase A 2 : preferential hydrolysis of acute phase HDL.

“…The sPLA 2 also did not affect the sphingomyelins present in the NHDL, APHDL, and LDL. The spingomyelins of LDL have been previously shown to be resistant to snake venom PLA 2 (27).…”

Section: Discussionmentioning

confidence: 99%

Lipoproteins are substrates for human secretory group IIA phospholipase A2: preferential hydrolysis of acute phase HDL

Pruzanski

Stefanski

Beer

et al. 1998

“…In many respects, the behavior of Lp[a] was very similar to that previously reported for PLA 2 -modified LDL, which also exhibited only modest structural changes in comparison to untreated LDL when studied by electron microscopic, circular dichroic, analytical ultracentrifugal, and small angle X-ray scattering techniques (22). Although the general structure of LDL is preserved by phospholipolysis, PLA 2 -LDL has been shown to exhibit decreased immunoreactivity in the C-terminal domain of apoB-100 as detected by competitive radioimmunoassay using a battery of apoB specific monoclonal antibodies (23). However, the potential relationship between this immunological change and the conformation of apoB-100 is not apparent.…”

Section: Discussionmentioning

confidence: 73%

“…No structural studies have been reported previously on Lp[a] digested by PLA 2 . On the other hand, there have been reports showing that phospholipolysis has only a minimal effect on the solution properties and structural stability of LDL (22), and decreases the immunoreactivity of epitopes located in the C-terminal domain of apoB (23). From the functional standpoint, recent reports have appeared showing that lipolysis by some phospholipases increases the in vitro binding of Lp[a] to lysine Sepharose (24,25) and components of the extracellular matrix (24).…”

Section: Lipoprotein[a] (Lp[a]mentioning

confidence: 99%

Effect of phospholipase A2 digestion on the conformation and lysine/fibrinogen binding properties of human lipoprotein[a]

Fless

Kirk

Klezovitch

et al. 1999

In vitro hydrolysis of human lipoprotein[a] (Lp[a]) by phospholipase A 2 (PLA 2 ) decreased the phosphatidylcholine (PC) content by 85%, but increased nonesterified fatty acids 3.2-fold and lysoPC 12.9-fold. PLA 2 -treated Lp[a] had a decreased molecular weight, increased density, and greater electronegativity on agarose gels. In solution, PLA 2 -Lp[a] was a monomer, and when assessed by sedimentation velocity it behaved like untreated Lp[a], in that it remained compact in NaCl solutions but assumed the extended form in the presence of 6-amino hexanoic acid, which was shown previously to have an affinity for the apo[a] lysine binding site II (LBS II) comprising kringles IV 5-8 . We interpreted our findings to indicate that PLA 2 digestion had no effect on the reactivity of this site. This conclusion was supported by the results obtained from lysine Sepharose and fibrinogen binding experiments, in the presence and absence of Tween 20, showing that phospholipolysis had no effect on the reactivity of the LBS-II domain. A comparable binding behavior was also exhibited by the free apo[a] derived from each of the two forms of Lp[a]. We did observe a small increase in affinity of PLA 2 -Lp[a] to lysine Sepharose and attributed it to changes in reactivity of the LBS I domain (kringle IV 10 ) induced by phospholipolysis. In conclusion, the extensive modification of Lp[a] caused by PLA 2 digestion had no significant influence on the reactivity of LBS II, which is the domain involved in the binding of apo[a] to fibrinogen and apoB-100. These results also suggest that phospholipids do not play an important role in these interactions. -Fless, G.

“…Most investigators believe that LDL particles must undergo modification before they become pathologic. Several postulated modifications include oxidation (32,33), glycation (34,35), and enzymatic degradation (36,37). A final answer as to which of these modifications imparts atherogenicity to LDL awaits further research, although it is plausible that each may contribute to atherosclerosis through a convergent mechanism, despite arising from different processes.…”

Section: Discussionmentioning

confidence: 99%

Analytical capillary isotachophoresis of total plasma lipoproteins: a new tool to identify atherogenic low density lipoproteins

Bittolo-Bon

Cazzolato

1999

Plasma low density lipoproteins from 20 patients were separated by capillary isotachophoresis (ITP). In each patient the apparent diameter of the predominant LDL peak on whole plasma was also determined by nondenaturing gradient gel electrophoresis. Furthermore the concentration of the more electronegatively charged in vivo oxidized LDL ؊ was accomplished using anion exchange high pressure liquid chromatography. By analytical capillary ITP of whole plasma lipoproteins, prestained with a lipophilic dye, LDL were separated into four subfractions. Usually, the predominant subfraction was the slow migrating LDL 4 , followed by LDL 3 , and then by the faster LDL 2 and LDL 1 . Slow migrating LDL 4 correlated negatively with plasma triglycerides and LDL ؊ and positively with plasma high density lipoprotein (HDL) cholesterol and with the LDL diameter, while the faster LDL 1 showed an inverse behavior. The LDL 1 ؉ LDL 2 to LDL 3 ؉ LDL 4 ratio showed a strong positive correlation with LDL ؊ concentration ( r ‫؍‬ 0.87; P Ͻ 0.001) and a highly significant inverse correlation with the LDL particle diameter ( r ϭ ؊ 0.74; P Ͻ 0.001). At least three highly atherogenic LDL that could be found in human plasma, namely oxidized, glycated and small-dense, are characterized by a greater electric charge. The LDL profile from capillary ITP and the relative prevalence of faster or slower migrating LDL fractions could indicate the presence of more atherogenic LDL.-Bittolo-Bon, G., and G. Cazzolato. Analytical capillary isotachophoresis of total plasma lipoproteins: a new tool to identify atherogenic low density lipoproteins.